From ae17ba727b0c9c4e2c49e6c67fea82a69e662415 Mon Sep 17 00:00:00 2001
From: "Dirk O. Kaar" <dok@dok-net.net>
Date: Sat, 20 Feb 2021 14:51:42 +0100
Subject: [PATCH] Extend swsertest for swapping HW and SW serial on USB to PC

---
 examples/swsertest/swsertest.ino | 79 ++++++++++++++++++++------------
 1 file changed, 50 insertions(+), 29 deletions(-)

diff --git a/examples/swsertest/swsertest.ino b/examples/swsertest/swsertest.ino
index 44ccad2..447bdfe 100644
--- a/examples/swsertest/swsertest.ino
+++ b/examples/swsertest/swsertest.ino
@@ -1,21 +1,28 @@
 // On ESP8266:
 // At 80MHz runs up 57600ps, and at 160MHz CPU frequency up to 115200bps with only negligible errors.
-// Connect pin 12 to 14.
+// Connect pin 13 to 15.
+// For verification and as a example for how to use SW serial on the USB to PC connection,
+// which allows the use of HW Serial on GPIO13 and GPIO15 instead, #define SWAPSERIAL below.
+// Notice how the bitrates are also swapped then between RX/TX and GPIO13/GPIO15.
+// Builtin debug output etc. must be stopped on HW Serial in this case, as it would interfere with the
+// external communication on GPIO13/GPIO15.
 
 #include <SoftwareSerial.h>
 
 #ifndef D5
 #if defined(ESP8266)
+#define D8 (15)
 #define D5 (14)
-#define D6 (12)
 #define D7 (13)
-#define D8 (15)
+#define D6 (12)
+#define RX (3)
 #define TX (1)
 #elif defined(ESP32)
+#define D8 (5)
 #define D5 (18)
-#define D6 (19)
 #define D7 (23)
-#define D8 (5)
+#define D6 (19)
+#define RX (3)
 #define TX (1)
 #endif
 #endif
@@ -26,33 +33,47 @@
 #define BAUD_RATE 57600
 #endif
 
-SoftwareSerial swSer;
+#undef SWAPSERIAL
+
+#ifndef SWAPSERIAL
+auto& usbSerial = Serial;
+SoftwareSerial testSerial;
+#else
+SoftwareSerial usbSerial;
+auto& testSerial = Serial;
+#endif
 
 void setup() {
-	Serial.begin(115200);
-	// Important: the buffer size optimizations here, in particular the isrBufSize (11) that is only sufficiently
-	// large to hold a single word (up to start - 8 data - parity - stop), are on the basis that any char written
-	// to the loopback SoftwareSerial adapter gets read before another write is performed.
-	// Block writes with a size greater than 1 would usually fail. Do not copy this into your own project without
-	// reading the documentation.
-	swSer.begin(BAUD_RATE, SWSERIAL_8N1, D5, D6, false, 95, 11);
-
-	Serial.println(PSTR("\nSoftware serial test started"));
-
-	for (char ch = ' '; ch <= 'z'; ch++) {
-		swSer.write(ch);
-	}
-	swSer.println();
+#ifndef SWAPSERIAL
+    usbSerial.begin(115200);
+    // Important: the buffer size optimizations here, in particular the isrBufSize (11) that is only sufficiently
+    // large to hold a single word (up to start - 8 data - parity - stop), are on the basis that any char written
+    // to the loopback SoftwareSerial adapter gets read before another write is performed.
+    // Block writes with a size greater than 1 would usually fail. Do not copy this into your own project without
+    // reading the documentation.
+    testSerial.begin(BAUD_RATE, SWSERIAL_8N1, D7, D8, false, 95, 11);
+#else
+    testSerial.begin(115200);
+    testSerial.setDebugOutput(false);
+    testSerial.swap();
+    usbSerial.begin(BAUD_RATE, SWSERIAL_8N1, RX, TX, false, 95);
+#endif
+
+    usbSerial.println(PSTR("\nSoftware serial test started"));
+
+    for (char ch = ' '; ch <= 'z'; ch++) {
+        testSerial.write(ch);
+    }
+    testSerial.println();
 }
 
 void loop() {
-	while (swSer.available() > 0) {
-		Serial.write(swSer.read());
-		yield();
-	}
-	while (Serial.available() > 0) {
-		swSer.write(Serial.read());
-		yield();
-	}
-
+    while (testSerial.available() > 0) {
+        usbSerial.write(testSerial.read());
+        yield();
+    }
+    while (usbSerial.available() > 0) {
+        testSerial.write(usbSerial.read());
+        yield();
+    }
 }